From: Nikola Cornij <nikola.cornij@amd.com>
Date: Wed, 9 May 2018 17:07:36 -0400
Subject: drm/amd/display: Optimize DP_SINK_STATUS_ESI range read on HPD
Git-commit: 3c8e4316a0bf6f65e8fbcf777abbc3b0e629e800
Patch-mainline: v4.19-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

DP_SINK_STATUS_ESI range data is not continual, but rather than
getting it in two AUX reads, it's quicker to read more bytes in a
AUX read and then memcpy the required fields (it's only 8 more
bytes to read).

Signed-off-by: Nikola Cornij <nikola.cornij@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c |   22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -1647,22 +1647,26 @@ static enum dc_status read_hpd_rx_irq_da
 			irq_data->raw,
 			sizeof(union hpd_irq_data));
 	else {
-		/* Read 2 bytes at this location,... */
+		/* Read 14 bytes in a single read and then copy only the required fields.
+		 * This is more efficient than doing it in two separate AUX reads. */
+
+		uint8_t tmp[DP_SINK_STATUS_ESI - DP_SINK_COUNT_ESI + 1];
+
 		retval = core_link_read_dpcd(
 			link,
 			DP_SINK_COUNT_ESI,
-			irq_data->raw,
-			2);
+			tmp,
+			sizeof(tmp));
 
 		if (retval != DC_OK)
 			return retval;
 
-		/* ... then read remaining 4 at the other location */
-		retval = core_link_read_dpcd(
-			link,
-			DP_LANE0_1_STATUS_ESI,
-			&irq_data->raw[2],
-			4);
+		irq_data->bytes.sink_cnt.raw = tmp[DP_SINK_COUNT_ESI - DP_SINK_COUNT_ESI];
+		irq_data->bytes.device_service_irq.raw = tmp[DP_DEVICE_SERVICE_IRQ_VECTOR_ESI0 - DP_SINK_COUNT_ESI];
+		irq_data->bytes.lane01_status.raw = tmp[DP_LANE0_1_STATUS_ESI - DP_SINK_COUNT_ESI];
+		irq_data->bytes.lane23_status.raw = tmp[DP_LANE2_3_STATUS_ESI - DP_SINK_COUNT_ESI];
+		irq_data->bytes.lane_status_updated.raw = tmp[DP_LANE_ALIGN_STATUS_UPDATED_ESI - DP_SINK_COUNT_ESI];
+		irq_data->bytes.sink_status.raw = tmp[DP_SINK_STATUS_ESI - DP_SINK_COUNT_ESI];
 	}
 
 	return retval;